Ru(OH)x supported on polyethylenimine modified magnetic nanoparticles coated with silica as catalyst for one-pot tandem aerobic oxidation/Knoevenagel condensation of alcohols and active methylene compounds

The immobilization of ruthenium species on polyethylenimine (PEI) modified magnetic nanoparticles coated with silica afford a multifunctional catalyst (Fe 3 O 4 @SiO 2 @PEI@Ru(OH) x ) for the aerobic oxidation/Knoevenagel condensation of alcohols and active methylene compounds. A wide scope of alcohols and malononitrile could be converted to their corresponding condensation products in excellent yields under mild conditions. This catalyst has advantages of leaching-free of ruthenium species and ease of recovery by an external magnet. The activity deactivation of the catalyst was investigated and was ascribed to the transformation of surface Ru 3+ to Ru 4+ in the process of aerobic oxidation of alcohols.